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Measurement of the Speech Intelligibility Inside Cars

The paper describes a measurement system developed for assessing the speech intelligibility inside car compartments. This relates directly to the understandability of the voices being reproduced through the radio receiving system (news, traffic info, etc.), but in the future it will be used also for assessing the direct speech communications between the passengers, and the performance of hands-free communication devices. The system is based on the use of two head and torso simulators, one equipped with an artificial mouth, the second equipped with binaural microphones. Only the second is used when the sound is being reproduced through the car's sound system. The MLS-based version of the STI method is used for performing the measurements, taking into account the effect of the background noise and the electro-acoustic propagation inside the compartment.